FILE PHOTO: A 3D-printed Facebook logo is seen in front of displayed stock graph Thomson Reuters LONDON (Reuters) - The world's biggest tech stocks were investors' top pick for the third straight month despite mounting worries over regulation, Bank of America Merrill Lynch's April fund manager survey found on Tuesday.

Sustained enthusiasm for tech stocks came against a backdrop of increasing anxiety about stock markets' resilience.

Allocation to equities fell to an 18-month low, the survey found, while some 40 percent of investors surveyed expected the stock market to peak in the second half of this year. Only 18 percent said the market had already peaked, however.

After a ratcheting up of protectionist rhetoric between the U.S. and China, investors said they saw the threat of a trade war as the biggest risk.